Doubled-faced tape

ABSTRACT

A double-faced tape according to which, in the case of fixing a liquid crystal display panel and a backlight module together using the double-faced tape, reflection of external light can be reduced as much as possible at the fixed parts, and moreover incident light from the backlight module can be reflected back toward the backlight module with high reflectance, whereby light from a light source can be used effectively; one face of the double-faced tape  10 A is made to be a low-reflectance face, and the other face is made to be a high-reflectance face or high-scattering face.

This application is a 371 of PCT/JP02/01650 Feb. 25, 2002.

1. Technical Field

The present invention relates to a double-faced tape suitable for fixinga liquid crystal display panel and a backlight module together.

2. Background Art

As shown in FIG. 5, a backlight module 1 of a liquid crystal displayapparatus comprises, broadly speaking, a light source 2 such as a coldcathode ray tube, a light-guiding plate 3 made of a transparent materialsuch as an acrylic plate, a reflector 4 that reflects light that hasbeen emitted from the light source 2 and inputs this light into an endface of the light-guiding plate 3, a reflecting plate 5 that is providedon a rear face of the light-guiding plate 3 (the face on the oppositeside to a face on which a liquid crystal display panel 20 is provided),a diffusing plate 6 that is provided on an upper face of thelight-guiding plate 3, and a prism sheet 7 that is provided, asrequired, on the diffusing plate 6. Here, the reflector 4, thereflecting plate 5 and the diffusing plate 6 are each fixed to thelight-guiding plate 3 by double-faced adhesive tape 10.

Moreover, the liquid crystal display panel 20 is fixed onto thediffusing plate 6 or the prism sheet 7 by double-faced adhesive tape 10,or else is fixed to a housing on the diffusing plate 6 or the prismsheet 7 using bolts or the like (not shown).

In such a liquid crystal display apparatus provided with a backlightmodule 1, in order to effectively utilize the light from the lightsource 2, it is preferable that, in the case that light from thebacklight module 1 strikes outside of the viewing area of the liquidcrystal display panel 20, this light is allowed to be reflected backtoward the reflecting plate 5 and to be then used inside the viewingarea.

On the other hand, when viewing such a liquid crystal display panel, itis undesirable for the brightness to suddenly increase in the vicinityof the viewing area, and hence it is required to prevent unwantedexternal light reflection, and thus make the brightness uniform, andmake the screen clear.

However, with the method in which the liquid crystal display panel 20and the backlight module 1 are fixed together using conventionaldouble-faced adhesive tape 10, it is not possible to fulfill theserequirements around the vicinity of the viewing area using simple means.

It is thus an object of the present invention to provide a novelfunctional double-faced tape according to which, in the case of fixing aliquid crystal display panel and a backlight module together using thedouble-faced tape, reflection of external light can be reduced as muchas possible at the fixed parts, and moreover incident light from thebacklight module can be reflected back toward the backlight module withhigh reflectance, whereby light from a light source can be usedeffectively.

DISCLOSURE OF THE INVENTION

To attain the above object, the present invention provides adouble-faced tape, wherein one face constitutes a low-reflectance face,and the other face constitutes a high-reflectance face orhigh-scattering face.

Moreover, the present invention provides, as a liquid crystal displayapparatus in which a liquid crystal display panel and a backlight moduleare fixed together using double-faced tape, a liquid crystal displayapparatus in which the liquid crystal display panel and the backlightmodule are fixed together by sticking the liquid crystal display panelto the low-reflectance face of the above-mentioned double-faced tape andsticking the backlight module to the high-reflectance face orhigh-scattering face.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a double-faced tape of the presentinvention;

FIG. 2 is a sectional view of a double-faced tape of the presentinvention;

FIG. 3 is a sectional view of a double-faced tape of the presentinvention;

FIG. 4 is a sectional view of a structure in which a liquid crystaldisplay panel and a backlight module are fixed together using adouble-faced tape of the present invention; and

FIG. 5 is a sectional view of a structure in which a liquid crystaldisplay panel and a backlight module are fixed together using aconventional double-faced tape.

BEST MODE FOR CARRYING OUT THE INVENTION

Following is a detailed description of the present invention withreference to the drawings. Note that in the various drawings, the samereference numeral represents identical or equivalent constituentelements.

FIG. 1 is a sectional view of an example of the double-faced tape of thepresent invention.

This double-faced tape 10A comprises a substrate 11 _(W) comprising awhite PET film, a black adhesive layer 12 _(B) forming a low-reflectanceface on one face of the substrate 11 _(W), and a transparent or whiteadhesive layer 13 _(W) forming a high-reflectance face or high-diffusionface on the other face of the substrate 11 _(W).

Here, means for making the PET film used as the substrate 11 _(W) bewhite include kneading a white paint into PET, using a foamed PET film,printing a white paint onto the PET film, and so on. In particular, if afoamed PET film is used, then surface uneveness can be formed on thesubstrate surface, and hence in the case of forming a transparentadhesive layer thereon, this face can be made to be a high-scatteringface.

The black adhesive layer 12 _(B) can be obtained by putting a black ordark-colored paint, dye, filler or the like into an adhesive resin madeof an acrylic acid ester or the like, and coating onto the substrate 11_(W). It is preferable to form the black adhesive layer 12 _(B) suchthat the visible light transmittance is not more than 0.1%.

The transparent or white adhesive layer 13 _(W) can be obtained bycoating a transparent adhesive resin made of an acrylic acid ester orthe like, or such a transparent adhesive resin into which has been put awhite paint, dye, filler or the like, onto the substrate 11 _(W). Inparticular, in the case of making the transparent or white adhesivelayer 13 _(W) itself have a light-scattering ability, it is preferableto put in a light-scattering filler such as TiO₂.

The double-faced tape 10A is useful in the case that low reflectance oflight is required of one face of the double-faced tape, and highreflectance or high scattering ability is required of the other face;for example, as shown in FIG. 4, in the case of fixing a liquid crystaldisplay panel 20 and a backlight module 1 together using thedouble-faced tape 10A, it is preferable for the black adhesive layer 12_(B) to be stuck to the liquid crystal display panel 20, and thetransparent or white adhesive layer 13 _(W) to be stuck to the backlightmodule 1. As a result, when viewing the liquid crystal display panel,the effective screen frame will be surrounded by a black framecomprising the black adhesive layer 12 _(B), and hence wavering of thescreen can be prevented. Moreover, in the case that light from thebacklight module 1 is incident on the part where the double-faced tape10A is stuck on, the high-reflectance face or high-scattering facecomprising the transparent or white adhesive layer 13 _(W) will reflectthis light back toward the backlight module 1, and hence this light canbe made to act as illuminating light that is incident inside the viewingarea; loss of light can thus be reduced. In particular, in the case thatthis face is constituted to be a high-reflectance face having a lowscattering ability, light reflected thereat will be reflected at thereflecting plate 5 of the backlight module 1, and then this reflectedlight will immediately exit on the inside of the viewing area withoutundergoing total reflection in the light-guiding plate 3, and hencethere will be a risk of a so-called white-out phenomenon occurring inwhich the screen brightness becomes excessively high; it is thuspreferable to constitute this face to be a high-reflectance face havinga high scattering ability, whereby the white-out phenomenon can beprevented.

The present invention also encompasses a liquid crystal displayapparatus in which a liquid crystal display panel 20 and a backlightmodule 1 are fixed together using the double-faced tape 10A in this way.

The double-faced tape of the present invention can be made to have anyof various forms, so long as one face thereof is made to have lowreflectance, and the other face is made to have high reflectance or highscattering ability.

For example, as with the double-faced tape 10B shown in FIG. 2, it ispossible to use a white PET film 11 a having a black printed face 11 bprovided thereon as a substrate 11, and provide a transparent adhesivelayer 12 _(T) on the black printed face 11 b.

Moreover, in the case of using a white PET film 11 a having a blackprinted face 11 b provided thereon as a substrate 11, it is possible toprovide a black adhesive layer 12 _(B) on the black printed face 11 b aswith the double-faced tape 10C shown in FIG. 3. As a result, the facecomprising the black adhesive layer 12 _(B) can be made to have a yetlower reflectance.

In addition, in the double-faced tape of the present invention, theadhesive layers on the two faces of the substrate may be replaced withbonding agent layers, with the bonding agent layers similarly being madeto have low reflectance, and high reflectance or high scatteringability.

Moreover, the substrate is not limited to being a PET film, but ratherany of various resin films, a nonwoven cloth or the like can be used.

INDUSTRIAL APPLICABILITY

If a liquid crystal display panel and a backlight module are fixedtogether using the double-faced tape of the present invention, thenreflection of external light can be reduced as much as possible at thefixed parts, and moreover incident light from the backlight module canbe reflected back toward the backlight module with high reflectance,whereby light from a light source can be used effectively.

1. A liquid crystal display apparatus, in which a liquid crystal displaypanel and a backlight module are fixed together by sticking the liquidcrystal display panel to the low-reflectance face of a double-facedtape, wherein one face constitutes a low reflectance face, and the otherface constitutes a high reflectance face or high scattering face andsticking the backlight module to the high-reflectance face orhigh-scattering face of the double-faced tape, an effective screen frameof the liquid crystal display panel being surrounded by a black framecomprising the double faced tape.
 2. A liquid crystal display apparatus,in which a liquid crystal display panel and a backlight module are fixedtogether by sticking the liquid crystal display panel to thelow-reflectance face of a double-faced tape, wherein one faceconstitutes a low reflectance face, and the other face constitutes ahigh reflectance face or high scattering face, the low reflectance facecomprises a black adhesive layer provided on a substrate, and stickingthe backlight module to the high-reflectance face or high-scatteringface of the double-faced tape, an effective screen frame of the liquidcrystal display panel being surrounded by a black frame comprising thedouble faced tape.
 3. A liquid crystal display apparatus, in which aliquid crystal display panel and a backlight module are fixed togetherby sticking the liquid crystal display panel to the low-reflectance faceof a double-faced tape wherein one face constitutes a low reflectanceface, and the other face constitutes a high reflectance face or highscattering face, the low reflectance face comprises a transparentadhesive layer provided on a black printed face of a substrate havingthe black printed face on one face thereof, and sticking the backlightmodule to the high-reflectance face or high-scattering face of thedouble-faced tape, an effective screen frame of the liquid crystaldisplay panel being surrounded by a black frame comprising the doublefaced tape.
 4. A liquid crystal display apparatus, in which a liquidcrystal display panel and a backlight module are fixed together bysticking the liquid crystal display panel to the low-reflectance face ofa double-faced tape wherein one face constitutes a low reflectance face,and the other face constitutes a high reflectance face or highscattering face, the high-reflective face or high-scattering facecomprises a white adhesive layer provided on a substrate and stickingthe backlight module to the high-reflectance face or high-scatteringface of the double-faced tape, an effective screen frame of the liquidcrystal display panel being surrounded by a black frame comprising thedouble faced tape.
 5. A liquid crystal display apparatus, in which aliquid crystal display panel and a backlight module are fixed togetherby sticking the liquid crystal display panel to the low-reflectance faceof a double-faced tape wherein one face constitutes a low reflectanceface, and the other face constitutes a high reflectance face or highscattering face, the high-reflectance face or high-scattering facecomprises a transparent adhesive layer provided on a substratecomprising white foamed PET film and sticking the backlight module tothe high-reflectance face or high-scattering face of the double-facedtape, an effective screen frame of the liquid crystal display panelbeing surrounded by a black frame comprising the double faced tape.